Echocardiography Exam 2 Practice Test

PISA relies on flow convergence proximal to a regurgitant orifice. As blood accelerates toward the orifice, the velocity increases until it reaches a defined aliasing velocity, creating an isovelocity surface whose near-hemispherical shape is the basis for a simple flow calculation. By measuring the radius r of that first-encountered aliasing surface on color Doppler and using the known aliasing velocity Va, you estimate the flow rate through the orifice with Q = 2π r^2 Va. This flow rate is then related to the regurgitant jet by dividing by the peak velocity of the regurgitant jet Vmax measured with continuous-wave Doppler, giving the effective regurgitant orifice area: EROA = Q / Vmax = (2π r^2 Va) / Vmax. In practice, this means you place the sample window to capture the flow convergence, measure the radius at the first aliasing contour, and apply the formula to obtain EROA and, subsequently, regurgitant volume. Common pitfalls to avoid include assuming the flow convergence forms a perfect hemisphere, since actual flow can be distorted by jet direction, LV geometry, or multiple jets; eccentric or laminar jets and misalignment of the Doppler beam can bias the measured radius and Va, leading to under- or overestimation of EROA; and mistimed or incorrect placement of the measurement plane or use of an inappropriate aliasing velocity can distort Q. Being mindful of these factors helps ensure the PISA estimate reflects the true regurgitant flow.